Primer assembly



Feb. 22, 1966 w. B. WOODRING ETAL 3,236,181

PRIMER ASSEMBLY Filed April 22, 1963 INVENTORS. WILL/AM B. WOODR/NGRICHARD J. SHELLNUTT MERTON L. ROBINSON PAUL S. FOSTER By w\ AT TORNEYUnited States Patent Ofitice 3,236,181 PRIMER ASSEMBLY William B.Woodring, Branford, Richard J. Shellnutt, Northrord, Merton L. Robinson,Woodbridge, and Paul S. Foster, Orange, Conn., assignors, by mesneassignments, to the United States of America as represented by theSecretary of the Army Filed Apr. 22, 1963, Ser. No. 274,632 7 Claims.(Cl. 102-45) This invention relates to ammunition primers forpercussively igniting primed cartridge cases and to an improved methodof so priming cartridge cases.

In center fire ammunition, which is characterized by a head structure ofmetal, among the important requirements are that the included parts,especially the anvil, be maintained in proper association to achieveignition reliably and effectively and that the structure at the primermust be able to resist the pressure developed when the primer burns.

Accordingly, an object of this invention is to provide a stronger headstructure at the primer in cartridge cases of all calibers, includingeven the smallest, where the problem of both elastic and plasticexpansion of the case faster than the expansion of the primer cup isaccentuated particularly when higher propellant pressures are employedin a cartridge case of small diameter, irrespective of the bulletcaliber.

Another object is providing a simplified primer of small size butadequate volume for effective priming.

Another object, therefore, is the provision of a new method of primingcartridges which will provide a simple and reliable primer assembledwith ease and economy.

Still another object is the provision of a new primer structure havingexceptional uniformity of dimensions and sensitivity and which willreliably ignite the priming composition with exact uniformity whileeffectively retaining the primers metallic components and the gasesresulting from the ignition.

These and other objects are attained by a novel con structionconstituting a significant improvement over the type of primer shown inUS. Patent Nos. 92,795 and 94,210, characterized by an anvil having aleg extending through the flash hole or vent in the base of the case.

Where these prior art primers have an anvil with a stem fittingrelatively loosely in the flash hole to adapt the cartridge forrepriming and reloading, the improvement of this invention involvesstaking a new and improved anvil configuration in a novel way in thehead of a case to obtain both longitudinal and lateral support for theanvil while maintaining the necessary communication at the flash holebetween the priming composition and the charge of propellant in thecharger case.

How this is done will become apparent from a description of a preferredembodiment with reference to the attached drawing in which:

FIG. 1 is a longitudinal sectional view of a base portion of a cartridgecase at the head;

FIG. 2 is a fragmentary and enlarged view taken on line IIII of FIGURE1.

Cartridge 1 has at its head a metal base 10, and joined thereto is theconventional cylindrical wall 11 which is integrally formed with thebase for containing the usual propellant charge. The solid base isformed with a central primerpocket 12 and has a perforated web portion13 between the pocket and the cartridge powder cavity. The perforationthrough the web portion is a central flash passage 14, forming a hole ofsmaller diameter than that of the pocket.

Emplaced within the head is the anvil 2 and the primer cup 3, the latterbeing held by frictional or other means, and being loaded with apercussion sensitive mix 4.

The anvil is disposed to extend into both the pocket and flash hole; ithas a shank 5 having substantially paral- 3,236,181 Patented Feb. 22,1966 lel sides extending over the full length of the passage 14. Shank 5is adapted to be firmly staked in the flash hole 14 by cutting into themetal of the web portion 13; for this purpose the shank is slightlytapered in width. One extremity is beveled at 6 to form a short guidemeans for aiding pressing of the anvil into the cartridge case. At theopposite end the anvil has a projecting point 8 for extension into theprimer cup and coaction with a. suitable primer mix 4. Between theseends, the anvil has an enlargement 7 providing a shoulder 9 foraccurate- 1y bottoming and positioning the anvil. Opposite the shoulderthe enlargement 7 is cut away on a bevel or a curve so as to minimizethe portion of the volume of the cup occupied by the anvil thusproviding a generous volume for receiving an adequate amount of theprimer mix, despite the fact that this construction is generallyadaptable for cartridges of small diameter at the head having a primerpocket and cup of reduced diameter.

In contrast to the conventional type of primer as shown in US. PatentNos. 208,589, Gardner; 962,888, Buell; and 1,571,510, Dickerman andwhere the anvil occupies around 40% of the primer cup volume in thistype of ammunition, the primer construction of this invention utilizesonly around 10% of the cup for reception of the anvil projection.

Where with such a relatively wide conventional primer it is necessary tohave a coned anvil involving blanking, bending, drawing, or swaging tomake the anvil point supported by two or more legs between a like numberof flash notches of the anvil, which must be press fitted into the cupin a precision assembly involving two small diameters held to very closetolerances, in contrast the relatively slender anvil 2 is merely blankedto final finished shape and size and pressed into the flash hole 14 intofinal position rather than into the usual preassembly with the cup whichmust then be pressed in turn into the pocket. Thus, the problem oftolerances is largely eliminated and the primer is completed withremarkable uniformity by merely press fitting in the reduced diametercup 3 carrying mix 4 in a condition suitable for safe assembly.Dimensional variation from metal spring back and flexing is avoided.

As a result, the diameter of the cup 3 and pocket 12 can be reduced byabout a third to give more strength at the base 10. Even at higherpropellent powder pressures, dropped primers and leaky primers wereeliminated. The added metal grip on the anvil at web 13 makes forconsistent sensitivity and firing.

Where in the conventional primer the flame must flow in a circuitouspath around the wide spread configuration of the anvil before it reachesthe flash hole, the primer of this invention in contradistinction offersless obstruction to the passage of the flame straight from the cup tothe flash openings 15 and 16. Since this reduces the heat and energylost, the primer efliciency is improved.

The anvil shank 5 of this primer is of rectangular cross section, i.e.it is of a width in excess of the thickness, and its dimension of widthis substantially equal to the diameter of the flash hole 14, so thatdiagonally from A to C, or B to D, it is slightly in excess of the holediameter and will cut into the web 13 and stake itself rigidly uponbeing pressed into the flash hole to divide it into the two adequateopenings 15 and 16 left since the thickness from A to D, or from B to Cextends over only part of the diameter, preferably not more than 40% ofit, but not less than 30% of the diameter. For example, in a flash holehaving a diameter of about 0.060 of an inch, a thickness of a typicalanvil from 0.018 to about 0.020 of an inch was found satisfactorytogether with an anvil width of about 0.060 of an inch.

An anvil width about three (3) times its thickness rather loosely in theflash hole, the present primer anvil is not adapted to facilitateextraction of the exploded primer by pressing on the stem. Moreover, itavoids the obstruction frequently olfered by this type of prior artanvil, which at that time suggested the need for a tiny central flashpassage in the already minute stem of these anvils. Unlike the priorart, anvil 2 cannot tip to shut hole 14 and is anchored straight in thecase and anvil anchoring, independently of the anchorage of the cup 3,has the advantage of avoiding difficulties of preassembly, for example,either by crimping the cup in under the anvil head, or by precisionfitting of the anvil inside the cup. By staking, all desired accuracy,nevertheless, is achieved, together with consistent sensitivity.

For the best cutting or indenting to stake the anvil, the substantiallyparallel sides of shank 5 preferably are slightly tapered on a side at arate of about 1 in 40 giving an over all divergence of about 1 in 20from a width substantially equal to the flash hole diameter adjacentbeveled end 6 to the greatest excess adjacent shoulder 9.

For example, for a flash hole having a nominal diameter of about 0.060of an inch, the shank width varies from about 0.0600.061 of an inchadjacent end 6 to about 0.064-0.065 of an inch next to shoulder 9.

At the enlargement 7 there is no problem of clearance or fit in thepocket 12, because the width of the enlargement is made suflicientlysmaller than the pocket diameter. In a pocket having a diameter of 0.120of an inch, for example, the width of enlargement 7 is about 0.100 of aninch.

The anvil has a thickness less than any part of its width except that ofthe percussion projection 8. In any event, the cruciform anvil shown ispreferred.

What is claimed is:

1. A primer assembly comprising (a) a cartridge case having a propellantcavity and a head recessed and perforated to define, respectively, (1) aprimer pocket extending inwardly and peripherally to a thickness of webin said head and (2) a flash hole reduced laterally with reference tosaid pocket and having sides extending longitudinally over a length ofcommunication through said web between said cavity and pocket, said holedefining with said web at said pocket a transversely extending shoulder,

(b) a primer cup disposed in said pocket in opposed relation to saidflash hole, said cup having an outer end wall and a peripherallyextending side wall engaged in pocket sealing and retained relationshipwith the head of said case,

(c) an elongated anvil in engagement with said case in spaced relationwith respect to said end wall, said anvil having a percussion projectionon one end extending into said cup adjacent said end wall, a reducedextension forming a substantially parallel-sided blade on the oppositeend staked within said flash hole to provide said anvil engagement byindentation of said case by said extension at peripherally spacedintervals over substantially all of said length, said extension fillingonly part of said hole to provide flash openings peripherally spaced inalternation with said spaced indentation, said anvil having anenlargement intermediate said ends for seating of said anvil on said webover only part of said shoulder,

(d) and a charge of primer mix contained in said cup and substantiallyfilling the cup volume between said cup walls and said anvil.

2. The primer assembly of claim 1 wherein the anvil has a cruciformshape and thickness less than any part of its width, exclusive of thepercussion projection.

3. The primer assembly of claim 1 wherein the anvil extension forms ablade slightly tapered over the length of engagement with the web on apair of opposite sides and sharply tapered at the tip to facilitatestaking the anvil in the flash hole.

4. The primer assembly of claim 3 wherein the blade is longer than theflash hole length and wherein the tip extends into the propellantcavity.

5. The primer assembly of claim 1 wherein the primer anvil occupies notmore than about 10% of the cup volume and wherein the charge of primermix between the cup walls and said anvil occupies up to of said volume.

6. A primer assembly comprising (a) a cartridge case having a propellantcavity and a head centrally recessed and perforated to define,respectively, (1) a round primer pocket extending inwardly andperipherally to a thickness of web in said head and (2) a round flashhole reduced laterally with reference to said pocket and having straightsides extending longitudinally over a length of communication throughsaid web between said cavity and pocket, said hole defining with saidWeb at said pocket a transversely extending shoulder,

(b) a primer cup disposed in said pocket in opposed relation to saidflash hole, said cup having an outer end wall and a circumferentiallyextending side wall engaged in pocket sealing and retained relationshipwith the head of said case and in spaced relation from said shoulder,

(c) an elongated cruciform anvil of sheet metal in engagement with saidcase in spaced opposed relation with respect to said end wall, saidanvil having a percussion projection on one end extending centrally intosaid cup adjacent said end wall, a reduced extension forming a blade onthe opposite end of rectangular cross section centrally staked withinsaid flash hole to provide said anvil engagement by indentation of saidcase by said extension at peripherally spaced intervals over all of saidlength, said extension filling only part of said hole centrally toprovide flash openings peripherally spaced in alternation with saidspaced indentation, said anvil having an enlargement intermediate saidends for seating of said anvil on said web over only part of saidshoulder,

(d) and a charge of primer mix contained in said cup and substantiallyfilling the cup volume between said cup walls and said anvil.

7. The primer assembly of claim 6 wherein said blade extension has athickness of at least 30% but not more than 40% of the flash holediameter and a width at least that of said diameter for indentation on apair of opposite sides of said extension.

References Cited by the Examiner UNITED STATES PATENTS 92,795 7/ 1869Chaudun 10245 94,210 8/ 1869 Hotchkiss 10245 226,117 3/1880 Saget 10244462,611 11/1891 De Sparre 10244 572,888 12/1896 Gardner 10245 2,388,09410/ 1945 Snell 10244 FOREIGN PATENTS 507,651 1939 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner. SAMUEL FEINBERG, Examiner.

R. F. STAHL, Assistant Examiner.

1. A PRIMER ASSEMBLY COMPRISING (A) A CARTRIDGE CASE HAVING A PROPELLANTCAVITY AND A HEAD RECESSED AND PERFORATED TO DEFINE, RESPECTIVELY, (1) APRIMER POCKET EXTENDING INWARDLY AND PERIPHERALLY TO A THICKNESS OF WEBIN SAID HEAD AND (2) A FLASH HOLE REDUCED LATERALLY WITH REFERENCE TOSAID POCKET AND HAVING SIDES EXTENDING LONGITUDINALLY OVER A LENGTH OFCOMMUNICATION THROUGH SAID WEB BETWEEN SAID CAVITY AND POCKET, SAID HOLEDEFINING WITH SAID WEB AT SAID POCKET A TRANSVERSELY EXTENDING SHOULDER,(B) A PRIMER CUP DISPOSED IN SAID POCKET IN OPPOSED RELATION TO SAIDFLASH HOLE, SAID CUP HAVING AN OUTER END WALL AND A PERIPHERALLYEXTENDING SIDE WALL ENGAGED IN POCKET SEALING AND RETAINED RELATIONSHIPWITH THE HEAD OF SAID CASE, (C) AN ELONGATED ANVIL IN ENGAGEMENT WITHSAID CASE IN SPACED RELATION WITH RESPECT TO SAID END WALL, SAID ANVILHAVING A PERCUSSION PROJECTION ON ONE END EXTENDING INTO SAID CUPADJACENT SAID END WALL, A REDUCED EXTENSION FORMING A SUBSTANTIALLYPARALLEL-SIDED BLADE ON THE OPPOSITE END STAKED WITHIN SAID FLASH HOLETO PROVIDE SAID ANVIL ENGAGEMENT BY INDENTATION OF SAID CASE BY SAIDEXTENSION AT PERIPHERALLY SPACED INTERVALS OVER SUBSTANTIALLY ALL OFSAID LENGTH, SAID EXTENSION FILLING ONLY PART OF SAID HOLE TO PROVIDEFLASH OPENINGS PERIPHERALLY SPACED IN ALTERNATION WITH SAID SPACEDINDENTATION, SAID ANVIL HAVING AN ENLARGEMENT INTERMEDIATE SAID ENDS FORSEATING OF SAID ANVIL ON SAID WEB OVER ONLY PART OF SAID SHOULDER, (D)AND A CHARGE OF PRIMER MIX CONTAINED IN SAID CUP AND SUBSTANTIALLYFILLING THE CUP VOLUME BETWEEN SAID CUP WALLS AND SAID ANVIL.